Streptococci

From IKE
Jump to: navigation, search

Colby notes

  • Gamma-haemolytic group is inappropriate nomenclature. What they really want to say is non-haemolytic streptococci.
  • fundamental point:
    • Toxic Shock Syndrome - caused by Staphlycoccus aureus (TSS-T1)
    • Scarlet Fever - caused by Streptycoccus pyogenes
    • Both have similiar clinical presentations, but recently there's been some garbage floating around about "streptococcal TSS" and "staphylococcal scarlet fever", neither of which exists.
  • haemolytic, Lancefield, biochemical and Linean taxonomies represent an evolution in classification. For example, beta-haemolytic strep became group A beta-haemolytic strep which today is called Streptococcus pyogenes. The confusing thing is that all of these are still used!
  • note, however, that there isn't always a correlation between the groups; for example, Group C consisted of three different types of strep, (i.e., the group was less precise than the biochemical classifications)
  • Important: If there are two patients with strep in the same room, the physician should know specifically which species (not just group) they are each infected with.
  • Streptococcus viridans - no Lancefield antigen and alpha haemolytic. By this definition, Streptococcus pneumoniae should be classified under this group, but by convention it is not
  • Streptococcus pneumoniae - usually not acquired as a disease. It is usually acquired as normal flora incorporated into the oropharynx, then spreads endogenously when given the chance
  • Clinically, glomerulonephritis and Rheumatic fever are both post-strep diseases which are immune-mediated, but both have vastly different outcomes
  • Glomerulonephritis is propagated by certain nephrotic strains that, by random luck of the draw, infect a host and wipe out the kidneys. The infection can't be prevented by rapid treatment and does not require a change in susceptibility. (?? I may have misheard)
  • By comparison, Rheumatic fever only arises from repeated strep pharyngitis attack, where strep surface antigens react with endothelial antigens formed from repeated infections. different people are thus more susceptible than others but the condition can be treated aggressively with antibiotics.

Resources

  • Steprococcus Handout (DOC | PDF)